Johnson was born
Los Angeles, and raised in
Oak Park/
Agoura (which he moved to when he was in fifth grade), a suburban town about 30 miles north of Los Angeles. Johnson attended
Oak Park High School his freshman year before transferring to
Notre Dame High School in
Sherman Oaks, California. He earned Parade, PrepStar, Football News and USA Today All-America first-team honors as a senior. Johnson recorded 104 tackles, including 32 for loss, and 17 sacks as a senior for the Knights while also setting school records for career sacks (61), tackles for loss (77), forced fumbles (14), and blocked punts (five). Before attending Notre Dame High School, Johnson played for his hometown of Oak Park, California for one year, playing junior varsity football and varsity basketball. ==College career==